Question: The average age of the three Wilson children is 7 years. If the two younger children are 4 years old and 7 years old, how many years old is the oldest child?
Solution: Let the age of the oldest child be $x$. We are told that $\frac{4 + 7 + x}{3} = 7$. Multiplying by 3, we see that $11 + x = 21$. We conclude that $x = \boxed{10}$.